Cant believe I missed this thread last year when I was reading up on stuff ....
Compared to you fellas ... Im a relative newcomer to jeeps.
Bought a new TJ in 97 ... and as I expected ... Its running temps were typical of an american vehicle ... more suited to northern hemisphere winters than weather down here.
Rather than wasting a heap of money modifying everything ... It got a lower rated thermostat and had little siestas at midday instead of pushing its cooling boundaries.
Did it "
overheat" ??? ... Only the once but 220'f/230'f was common in summer with
my use.
My concern was that it didnt just overheat to 250/260 ... It jumped from 220 to to those temps ... which confirmed my expectations that the cooling system just reaches a point where it cant sustain the higher operating temps & hot weather temps ... and gives up.
120,000 reasonably trouble free miles and 5yrs later it got swapped for a 2nd hand 97 OBDII XJ ... which got a total cooling system rebuild/cleanout/ test at time of purchase.
What a mongrel thing !!! ... even with a new stock factory cooling system it needed bigger midday naps than the TJ ... So it too got a lower rated thermostat ..... and 1/2" bonnet (
hood) spacers / fan over-ride switch ... end result being ... slightly lower running temp for daily driving ... and those "
designed" temps, everyone goes on about ... under load, with some occasional spikes.
Now in a second used 97/98 OBDII XJ ... Initially persisted with the previous setup ... but have taken some more interest in the "
design" and monitored the performance of the stock system.
Sit down everybody ... take a big breathe and hang onto your sofas.
THE XJ COOLING SYSTEM SUX ....... :laugh2:
The trick is in knowing why ........... And all the answers are out there. It all just depends on what YOU want to do about it.
Basically tho, it is only barely adequate ... when in good condition.
All of the components need to be in good order ... ALL of the time.
If "
adequate" is good enough for your vehicle use / operating area ... Then you shouldnt have any major XJ cooling issues ... especially if the factory addressed some of the "
overheating" issues with the factory options - on
your vehicle.
Poor maintenance as many have already stated is the main problem, altho there are plenty of other contributing factors e.g.
Gearbox type, ...
a poll on that one would be most beneficial and interesting.
Anti-Freeze mix ratios,
Fuel type and quality,
Crowded engine bay ...
It was meant to have a V6/4cyl -remember
Relying on a bunch of
variable things like clutch fans/radiator/weather instead of just the engine heat control device (thermostat) to maintain a minimum running temp,
Ambient weather chill factor on the radiator,
Quality of replacement parts,
... and the list goes on ..........
After much internet reading about everything from angle grinding half the engine bits off to fit electric fans and chopping holes in bonnets (hoods) ... This XJ now has the following;
Locally sold copper/brass radiator,
Locally sold 195'f thermostat that is
fully open, 12'f sooner than a factory thermostat,
but not a hi-volume flow thermostat
1/2" bonnet spacers,
with an airblocker in the middle, at the rear so it only vents at the corners and doesnt draw in air at speeds over 25mph
Bypassed AW4 gearbox in-tank radiator heat exchanger,
larger, proper cooler fitted in front of aircon core
Omix Ada stock replacement part, water pump and fan clutch,
Less than 50/50 antifreeze/water mix,
Factory fitted auxilliary electric fan.
And just like magic ... It runs at what it should run at with a 195'f thermostat fitted ....
195'f
Fuel use ... No discernable change
Open / Close Loop ... No change ... still happening at
68'f ...... as usual.
The only "
mod" being the raised bonnet ... all the other components are perishables anyway and need replacing on a "
regular" basis. Havent even needed to flick the fan over-ride switch yet.
As for the reason for the AW4 radiator heat exchanger bypass ... Chryslers "
designers" were
sooooo clever - they put in it the hot side of the radiator for the sales market down here ... No wonder I cooked the last AW4 ... :banghead:
Something as critical as a vehicle cooling system should never be just "
adequate" ..... as the XJ one is.
An adequate cooling system is about as handy as finger tight wheel nuts/lugs.
It should have some reserve cooling facility for those "
heavy duty" situations ... which, with some simple, cost effective changes - can be provided.
For those that "
believe" 210'f is a designed temp, ideal for every engine circumstance of operation .... a better radiator,
known, good condition, pump, fan etc ... and the slow opening factory thermostat should maintain that temp I guess.
:cheers:
